I lived in an ex-council flat in London for 12 years, and I simply don't recognise the issues some people (who have probably no experience of actually owning ex-council) are talking about above. My service charges were not high at all (too long ago to remember what it was) and actually the council is very highly regulated about what it can charge for major works, so you are actually far safer from unreasonable demands for money than you are with unregulated private management companies. They have to get a certain number of bids, prove that they are reputable and not brown paper envelope deals, as an owner you have the right to raise objections if you think the costs are unreasonable.
That said, mine was a relatively small brick-built block, with no lift and I understand lift maintenance is one of the biggest costs that can come and hit you in a block of flats. Admittedly you have no control of what is done when with council blocks - so you can't argue that the roof, double-glazing or whatever is done sooner rather than later, but you do get a lot of warning of any upcoming works because the processes are so convoluted around having to have notice of intent, notice they are going out for bids - it goes on quite a long time (years!) before the work is done and then you are billed afterwards.
I also found that having the council as the freeholder was brilliant for availability and accessibility. As a leaseholder I had access to the same helplines etc as the council tenants, and the council have maintenance teams that can fix issues quickly without having to go around finding private contractors and all that complexity. When the flat above me had a leak that came into my kitchen, we both contacted the council who just sent their maintenance guys round within hours and sorted.
Council flats are always less popular, which means you get less when you sell than you would for a private flat of a similar size/location. But you will also have bought it at a lower price in the first place, so it's not really the right comparison to make. As above, you just need to think of them as "good value" for the buyer.